This disclosure relates to a heat exchanger system for a vehicle. The heat exchanger system comprising at least one heat exchanger; a centrifugal fan assembly for improving the flow of air through the heat exchanger, the fan assembly comprising a rotatably mounted impeller with a plurality of impeller blades, and a rotatable inlet shroud for guiding the air flow entering the impeller; and a stationary inlet shroud located between the at least one heat exchanger and the fan assembly and configured for directing air exiting the at least one heat exchanger towards the inlet shroud of the fan assembly. The disclosure also relates to vehicle comprising such a heat exchanger system. The heat exchanger system according to the disclosure may typically used in vehicles such as automobiles, trucks, busses, construction vehicles, marine vehicles, etc.
As output power demand of combustion engines continues to increase so does the cooling effect required to prevent the combustion engines from over-heating. Improving and increasing the flow of air through the heat exchanger is one option for realising increased cooling effect of a machine cooling system. A fan assembly for a mobile machine cooling system having a centrifugal fan and reduced leakage is known U.S. Pat. No. 6,450,765 B1. There is however still need for improvements with respect to increased cooling and fan efficiency.
It is desirable to provide a heat exchanger system for a vehicle where the previously mentioned problem is at least partly avoided.
The disclosure concerns, according to an aspect thereof, a heat exchanger system for a vehicle. The heat exchanger system comprising at least one heat exchanger; a centrifugal fan assembly for improving the flow of air through the at least one heat exchanger, the fan assembly comprising a rotatably mounted impeller with a plurality of impeller blades, and a rotatable inlet shroud for guiding the air flow entering the impeller; and a stationary inlet shroud located between the at least one heat exchanger and the fan assembly and configured for directing air exiting the at least one heat exchanger towards the inlet shroud of the fan assembly.
The disclosure, according to an aspect thereof, is characterized in that the fan assembly further comprising a stator with a plurality of stationary stator blades located radially or semi-radially outside the impeller for conversion of fluid dynamic pressure to fluid static pressure of the air flow.
It is desirable to increase the static efficiency provided by the fan assembly because the air flow through the heat exchanger generated by the fan assembly is directly coupled to the static pressure difference before and after the heat exchanger. An increased static pressure difference generally results in increased through flow of air, such that improved cooling effect is obtained. Since the total pressure of any point of an air flow is the sum of static pressure and dynamic pressure, the static pressure of a point of the air flow can be increased by decreasing the dynamic pressure of the air flow at that point. Static pressure can be considered representing the potential energy put into the system by the fan. Dynamic pressure, also referred to as velocity pressure, is the kinetic energy of a unit of air flow in an air stream, and is a function of air flow speed and density. Consequently, by reducing the speed of the air flow the static pressure of the air flow increases. Conversion of air flow dynamic pressure into air flow static pressure is realised partly by recovering swirl energy (rotating flow velocity pressure) and partly by controlled radial diffusion of the outlet air flow. By straightening the air flow downstream of the impeller the rotational component of air movement caused by the rotation of the impeller is reduced, such that the total kinetic energy of the outlet flow is reduced, and by increasing the flow area in the downstream flow direction through the stator the flow speed is decreased and the static pressure increased correspondingly. Consequently, the cooling efficiency of the heat exchanger system is improved.
According to an aspect of the disclosure, an elastic seal is provided for sealing the gap between the stationary inlet shroud and fan assembly. The elastic seal is provided between two non-rotating members of the heat exchanger system. The stationary inlet shroud is relatively rigidly mounted to a chassis of the vehicle, whereas the fan assembly is mounted to the combustion engine of the vehicle. The combustion engine depending in its design, configuration and setting will generate more or less strong vibrations, and the chassis sometimes exhibit relatively strong vibrations due to driving on uneven roads. Consequently, the combustion engine is generally mounted to the chassis via elastic engine mounts, which serve to absorb much of the vibrations and to prevent the vibrations from being transmitted to and from the chassis for reasons of noise reduction and driver comfort. However, as a result of the elastic engine mounting, the relatively large amplitude vibrations and motion may occur between the engine and chassis. Moreover, since the fan assembly is generally powered mechanically by the crankshaft of the combustion engine the fan assembly is generally mounted to the engine. As a result, the gap between the stationary inlet shroud and fan assembly will exhibit relatively large dimensional variations. The elasticity of the elastic seal enables the seal to provide a high sealing capacity despite the potentially large relative motion of the stationary inlet shroud and the fan assembly. The elastic seal may exhibit corrugations or bellows for improved flexibility. The purpose of the elastic seal is to prevent air from outside the stationary inlet shroud from entering being sucked into the fan assembly. Thereby, leakage into the fan assembly is reduced and more air will instead be forced to pass through the heat exchanger for improved cooling efficiency.
According to an aspect of the disclosure, the elastic seal is fastened to at least one of the stationary inlet shroud and the member mounted to the propulsion source. The elastic seal may be fastened by means of any type of mechanical fastener, such as screws, rivets, clamping members, etc., and/or by an adhesive, and/or by welding, heat bonding, etc. The elastic seal may be fastened to one of the stationary inlet shroud and the member mounted to the propulsion source and simply abutting the other part with pretension, or fastened to both parts.
According to an aspect of the disclosure, the elastic seal is fastened to at least one of the stationary inlet shroud and the stator or a member fastened to the stator. Using the stator, or a member fastened to the stator as contact surface simplifies the design because the stator is located close to the stationary inlet shroud. The relatively small gap between the stationary inlet shroud and stator enables a more robust and reliable elastic seal mounting. The member fastened to the stator may for example be a stator sealing arrangement for sealing the gap between the stator and impeller, a stator shroud that extends forwards from the stator or a sealing arrangement that is supported by the stator shroud.
According to an aspect of the disclosure, the elastic seal is fastened to at least one of the stationary inlet shroud and a support member mounted to the propulsion source rearwards of the stator or a member fastened to said support member. If for some reason the stator cannot be used for sealing surface for the elastic seal then the support member mounted to the propulsion source rearwards of the stator may be used instead. The design is less robust because of the length of the axial support member, which also must pass over the outlet of the fan. Possibly, the support member may be attached to the engine using one or more attachment points in common with the fan assembly.
According to an aspect of the disclosure, the elastic seal comprises an elastic sealing sleeve. The elastic sealing sleeve is preferably made of rubber or a resilient plastic material.
According to an aspect of the disclosure, the radial gap between the impeller blades and stator blades is sealed by at least one sealing arrangement for preventing air leaking in or out of the gap. The radial gap may be provided with a sealing arrangement on the forward side and/or the rearward side of the fan assembly. Depending on the static pressure within the gap and the regions directly outside the gap, air will tend to leak in or out of the gap. The sealing arrangement is preferably realised by means of a non-contact sealing arrangement for avoiding friction and noise and wear of the parts. A non-contact sealing arrangement is a labyrinth-type sealing arrangement, where the leakage air is forced to change direction within the sealing arrangement at least one time. Alternatively, a contact sealing arrangement may be implemented, for example by means of a brush or other sliding-type sealing arrangements.
According to an aspect of the disclosure, the fan assembly inlet is sealed by at least one sealing arrangement for preventing air leaking into the fan assembly, wherein the sealing arrangement is arranged to seal a gap between the rotatable inlet shroud and a member mounted to the propulsion source. Since both the rotatable inlet shroud and said member are mounted to the propulsion source, their internal relative motion will be relatively small, such that a sealing arrangement having small dimensional tolerances can be implemented. In a non-contact sealing arrangement, such as a labyrinth-type sealing arrangement, the sealing performance is directly dependent on how small the air leakage path is. A non-contact sealing arrangement designed for small dimensional tolerances will consequently have a higher sealing performance than a non-contact sealing arrangement designed for high dimensional tolerances.
According to an aspect of the disclosure, the sealing arrangement is arranged to seal a gap between the rotatable inlet shroud and a stator shroud that extends forwards from the stator. This design enables the same advantageous effect as the previous aspect of the disclosure, namely an improved sealing performance due to the fact that both the rotatable inlet shroud and the stator shroud are mounted to the propulsion source, thereby enabling the sealing arrangement to have small dimensional tolerances. Moreover, the stator shroud also shields the sealing arrangement from air outside of the stator, such that only air leaking out of the radial gap between the impeller and stator will reach the sealing arrangement, thereby significantly reducing the possible leakage flow.
According to an aspect of the disclosure, the at least one sealing arrangement is of a labyrinth-type sealing arrangement. This type of seals as non-contact type seals that exhibits zero frictional losses and wear when correctly installed.
According to an aspect of the disclosure, the at least one labyrinth-type sealing arrangement of the heat exchanger system is configured for enabling axial mounting and/or dismounting of the stator and impeller. By arranging the labyrinth-type sealing arrangement properly it can be mounted merely be sliding the parts axially towards each other. This enables simplified single-piece design of the labyrinth-type sealing arrangement that otherwise must be divided in an axial plane into at least two parts for being assembled. Furthermore, of two or more labyrinth-type sealing arrangements are provided, for example also for sealing the radial gap between the impeller and stator, then axially consecutive labyrinth-type sealing arrangements must be have a consistent increasing or consistent decreasing radial offset from a rotational axis of the fan assembly.
According to an aspect of the disclosure, flow straightening devices are provided for straightening any air flow leaking out from the radial gap between the impeller blades and stator blades and back into the inlet air flow upstream of the impeller. The leakage flow out of the radial gap has except for an axial flow direction additionally a rotational swirl component due to the rotation of the impeller. The inlet flow from the heat exchanger into the impeller has however a more or less pure axial flow. For minimising any potentially negative effects on fan assembly efficiency due to flow distortions upstream of the impeller the rotational swirl component is reduced by means of the flow straightening devices. These may comprise a plurality of substantially axial or slightly curved blades that are located within the leakage air flow.
According to an aspect of the disclosure, sliding contact members made of rubber or plastic material are provided between the impeller and the stator, or any parts that are fastened or associated with the impeller and the stator, for preventing undesired noise and vibrations during occurrences of contact with each other.
According to an aspect of the disclosure, the impeller further comprises a back plate for structurally connecting the rotatable blades with a rotatable shaft of the impeller. The back plate may have a disc-shape arranged in a radial plane for a compact design, or a conical shape.
According to an aspect of the disclosure, the heat exchanger is arranged such that air flow during use of the heat exchanger system is configured to flow through the heat exchanger in a direction substantially coaxial with rotational axis of the impeller.
According to an aspect of the disclosure, the stator shroud is integrally formed with stator. This design tends to provide less total weight, reduced manufacturing costs and improved robustness.
According to an aspect of the disclosure, the rotatable inlet shroud is integrally formed with the impeller. This design tends to provide less total weight, reduced manufacturing costs and improved robustness
According to an aspect of the disclosure, the rotatable inlet shroud forms together with a side portion of the impeller a U-shaped cross-section that is open towards the radial outside. Air flowing towards the inlet of the impeller will thus be guided around the U-shaped cross-section with low flow distortion due to the rounded form, such that high fan efficiency can be maintained.
According to an aspect of the disclosure, the stator is divided in an axial plane into at least two parts. This enables mounting and dismounting of the impeller in a radial plane without disassembly of the impeller.